/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.tsfile.utils;

public class Murmur128Hash {

    private Murmur128Hash() {
        // util class
    }

    /**
     * get hashcode of value by seed
     *
     * @param value value
     * @param seed  seed
     * @return hashcode of value
     */
    public static int hash(String value, int seed) {
        return (int) innerHash(value.getBytes(), 0, value.getBytes().length, seed);
    }

    /**
     * get hashcode of two values by seed
     *
     * @param value1 the first value
     * @param value2 the second value
     * @param seed   seed
     * @return hashcode of value
     */
    public static int hash(String value1, long value2, int seed) {
        return (int)
                innerHash(
                        BytesUtils.concatByteArray(value1.getBytes(), BytesUtils.longToBytes(value2)),
                        0,
                        value1.length() + 8,
                        seed);
    }

    /**
     * Methods to perform murmur 128 hash.
     */
    private static long getBlock(byte[] key, int offset, int index) {
        int i8 = index << 3;
        int blockOffset = offset + i8;
        return ((long) key[blockOffset] & 0xff)
                + (((long) key[blockOffset + 1] & 0xff) << 8)
                + (((long) key[blockOffset + 2] & 0xff) << 16)
                + (((long) key[blockOffset + 3] & 0xff) << 24)
                + (((long) key[blockOffset + 4] & 0xff) << 32)
                + (((long) key[blockOffset + 5] & 0xff) << 40)
                + (((long) key[blockOffset + 6] & 0xff) << 48)
                + (((long) key[blockOffset + 7] & 0xff) << 56);
    }

    private static long rotl64(long v, int n) {
        return ((v << n) | (v >>> (64 - n)));
    }

    private static long fmix(long k) {
        k ^= k >>> 33;
        k *= 0xff51afd7ed558ccdL;
        k ^= k >>> 33;
        k *= 0xc4ceb9fe1a85ec53L;
        k ^= k >>> 33;
        return k;
    }

    private static long innerHash(byte[] key, int offset, int length, long seed) {
        final int nblocks = length >> 4; // Process as 128-bit blocks.
        long h1 = seed;
        long h2 = seed;
        long c1 = 0x87c37b91114253d5L;
        long c2 = 0x4cf5ad432745937fL;
        // ----------
        // body
        for (int i = 0; i < nblocks; i++) {
            long k1 = getBlock(key, offset, i * 2);
            long k2 = getBlock(key, offset, i * 2 + 1);
            k1 *= c1;
            k1 = rotl64(k1, 31);
            k1 *= c2;
            h1 ^= k1;
            h1 = rotl64(h1, 27);
            h1 += h2;
            h1 = h1 * 5 + 0x52dce729;
            k2 *= c2;
            k2 = rotl64(k2, 33);
            k2 *= c1;
            h2 ^= k2;
            h2 = rotl64(h2, 31);
            h2 += h1;
            h2 = h2 * 5 + 0x38495ab5;
        }
        // ----------
        // tail
        // Advance offset to the unprocessed tail of the data.
        offset += nblocks * 16;
        long k1 = 0;
        long k2 = 0;
        switch (length & 15) {
            case 15:
                k2 ^= ((long) key[offset + 14]) << 48;
                // fallthrough
            case 14:
                k2 ^= ((long) key[offset + 13]) << 40;
                // fallthrough
            case 13:
                k2 ^= ((long) key[offset + 12]) << 32;
                // fallthrough
            case 12:
                k2 ^= ((long) key[offset + 11]) << 24;
                // fallthrough
            case 11:
                k2 ^= ((long) key[offset + 10]) << 16;
                // fallthrough
            case 10:
                k2 ^= ((long) key[offset + 9]) << 8;
                // fallthrough
            case 9:
                k2 ^= key[offset + 8];
                k2 *= c2;
                k2 = rotl64(k2, 33);
                k2 *= c1;
                h2 ^= k2;
                // fallthrough
            case 8:
                k1 ^= ((long) key[offset + 7]) << 56;
                // fallthrough
            case 7:
                k1 ^= ((long) key[offset + 6]) << 48;
                // fallthrough
            case 6:
                k1 ^= ((long) key[offset + 5]) << 40;
                // fallthrough
            case 5:
                k1 ^= ((long) key[offset + 4]) << 32;
                // fallthrough
            case 4:
                k1 ^= ((long) key[offset + 3]) << 24;
                // fallthrough
            case 3:
                k1 ^= ((long) key[offset + 2]) << 16;
                // fallthrough
            case 2:
                k1 ^= ((long) key[offset + 1]) << 8;
                // fallthrough
            case 1:
                k1 ^= (key[offset]);
                k1 *= c1;
                k1 = rotl64(k1, 31);
                k1 *= c2;
                h1 ^= k1;
                break;
            default: // 0
                // do nothing

        }
        // ----------
        // finalization
        h1 ^= length;
        h2 ^= length;
        h1 += h2;
        h2 += h1;
        h1 = fmix(h1);
        h2 = fmix(h2);
        h1 += h2;
        h2 += h1;
        return h1 + h2;
    }
}
